Nobel Prize in Medicine Goes to Two U.S. Scientists

Biologists Andrew Z. Fire and Craig C. Mello will split the 2006 Nobel Prize in Physiology or Medicine for their work uncovering how certain genes in the body are inactivated.

The Nobel Assembly at the Karolinska Institute in Stockholm, Sweden, announced today that Fire, of Stanford University School of Medicine in California, and Mello, of the University of Massachusetts Medical School in Worcester, will each receive half of the prize, worth 10 million Swedish kronor (1.4 million U.S. dollars).

DNA holds the information needed to build all the proteins that make life possible. The information in a gene is first copied into a molecule known as mRNA (messenger RNA), which is then used as a template for making a protein (get a genetics overview.)

But unlike DNA, which generally exists only as a double-stranded molecule with two matching sides, mRNA is single-stranded.

Fire and Mello found that injecting a cell with the matching strand for a certain mRNA silences all expression of the associated gene—the protein is simply not made. The scientists reported their discoveries in a 1998 issue of the journal Nature.

The matching strand binds to the target RNA to create a double-stranded RNA molecule, similar to DNA.

This double-stranded RNA, scientists later discovered, is destroyed by a set of proteins as a natural defense mechanism against viruses, as well as a tool to regulate the expression of certain genes.